This invention relates generally to the treatment of diseased or traumatized intervertebral discs, and more particularly, to the use of engineered disc tissues in conjunction with such treatment.
Intervertebral discs provide mobility and a cushion between the vertebrae. At the center of each disc is the nucleus pulposus which, in the adult human, is composed of cells and an insoluble extracellular matrix which is produced by the nucleus itself. The extracellular matrix is composed of collagen, proteoglycans, water, and noncollagenous proteins.
The cells of the nucleus pulposus have chondrocyte-like features. Blood vessels do not course into the nucleus pulposus. Rather, the cells of the nucleus pulposus of the adult human obtain nutrients and eliminate waste by diffusion through blood vessels in the end plates of the vertebrae adjacent to the disc.
The nucleus pulposus is surrounded by the annulus fibrosis, which is composed of cells (fibrocyte-like and chondrocyte-like), collagen fibers, and non-fibrillar extracellular matrix. The components of the annulus are arranged in 15-25 lamellae around the nucleus pulposus.
To date, the treatment of degenerative disc disease has relied for the most part on eliminating the defective disc or disc function. This may be accomplished by fusing the vertebra on either side of the disc. In terms of replacement, most prior-art techniques use synthetic materials to replace the entire disc or a portion thereof. My pending U.S. patent application Ser. No. 09/415,382 discloses disc replacement methods and apparatus using synthetic materials.
Unfortunately, disc replacement using synthetic materials does not restore normal disc shape, physiology, or mechanical properties. Synthetic disc replacements tend to wear out, resulting in premature failure. The problems associated with the wear of prosthetic hip and knees are well known to those skilled in orthopedic surgery. The future of treating degenerative disc disease therefore lies in treatments which preserve disc function. If disc function could be restored with biologic replacement or augmentation, the risk of premature wear out would be minimized, if not eliminated.
Although transplantation of living cells risks rejection by graft host reaction, this invention broadly recognizes that transplantation of the extracellular matrix of the nucleus pulposus is unlikely to incite a graft host reaction. In the preferred embodiment, autograft nucleus pulposus cells are harvested, cultured, then added to nucleus pulposus extracellular matrix obtained from recently deceased humans or animals. The combined nucleus pulposus material is then introduced into the injured or diseased disc.
The cells or engineered tissues may be introduced using any surgical technique, including percutaneous or laparoscopic approaches. As one delivery mechanism, a passageway may be formed through the annulus fibrosis, with the cells or engineered disc tissue being introduced into the disc through the passageway. In particular, the engineered disc tissue may be morselized and injected into the disc with a needle and syringe or through a small cannula.
The method of the invention may further include the step of adding one or more therapeutic substances to the cells prior to transplantation. Such therapeutic substances could include culture media, growth factors, differentiation factors, hydrogels, polymers, antibiotics, anti-inflammatory medications, immunosuppressive medications, or any useful combination thereof.